Method of controlling a sintering process having a cooling zone

ABSTRACT

The present invention relates to a method of controlling a reduction in a temperature of sintered ores in a belt-shaped sintering machine, in which sintered ores as completely sintered are cooled as they are on a pallet to reduce the temperature of said sintered ores so as to have cracks in the sintered layer in the vertical direction in the final period of the cooling.

United States Patent [191 Tsujihata et al.

[ June 11, 1974 METHOD OF CONTROLLING A SINTERING PROCESS HAVING A COOLING ZONE [76] Inventors: Keiji Tsujihata, 21-7, 2-chome,

Nishiogi-kita, Suginami-ku, Tokyo; Yasuhiro Sawada, 26, 3-chome, Sakae-ch0, Euchu City, Tokyo; Yasushi Ishikawa, c/o Yawata-Works, Yawata Iron & Steel Co., Ltd., 1-1, Edamitsu-cho, Yawata-ku, Kitakyushu City, Fukuoka Prefecture; Mitsuteru Matsubara, c/o Yawata-Works,

' Yawata lron & Steel Co., 1-1,

Edamitsu-cho, Yawata-ku, Kitakyushu City, Fukuoka Prefecture; Minoru Iwata, c/o Yawata-Works, Yawata iron & Steel Co., Ltd., 1-1, Edamitsu-cho, Yawata-ku, Kitakyushu City, Fukuoka Prefecture, all of Japan 221 Filed: on. s, 1971 21 Appl. No.: 186,759

Related US. Application Data [63] Continuation of Ser. No. 701,350, Jan. 29, 1968.

52 us. Cl. 75/5 [51] Int. Cl C21b 1/10 [58] Field of Search 75/5 [56] References Cited UNITED STATES PATENTS 3,024,101 3/1962 Erck et a1. 75/5 3,275,431 9/1966 Sawada 75/5 3,301,659 l/l967 Hanson et al 75/5 3,332,770 7/1967 Wendt, Jr. et alQ... 75/5 3,369,888 2/1968 Cruse, Jr 75/5 3,370,937 2/1968 Tsujihata et al.. 75/5 3,399,053 8/1968 Schutz et a1. 75/5 Primary Examiner-A. B. Curtis Assistant Examiner-C. F. LeFevour Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [5 7 ABSTRACT The present invention relates to a method of controlling a reduction in a temperature of sintered ores in a belt-shaped sintering machine, in which sintered ores as completely sintered are cooled as they are on a pallet to reduce the temperature of said sintered ores so as to have cracks in the sintered layer in the vertical direction in the final period of the cooling.

1 Claim, 4 Drawing Figures mm! 1 an SHEET NF 2 FIG.

FIG.4

L 45 INVENTORS Tsujihafa Yasuhiro Sawada Yasushi Ishikawa Mitsuteru Mafsubara Minoru I wafa Kejji METHOD OF CONTROLLING A SINTERING PROCESS HAVING A COOLING ZONE This is a continuation, of application Ser. No. 701,350 filed Jan. 29, 1968.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of controlling such belt-shaped sintering process as in a Dwight-Lloyd type sintering machine.

2. Description of the Prior Art The already generally adopted sintering process is such as is shown in FIG. 1. Its construction and operation are as follows. That is to say, a mixed raw material 1 to be sintered is fed into a charging hopper 2, is moved onto a sintering machine palette 9 through a sloping plate as indicated by arrows 4 by rotating a drum feeder 3 and is conveyed. The charge 8 is gradually moved in the direction indicated by the arrows 4 by the sintering machine palette 9, is ignited by an igniting device 6 and is moved to a discharging side while being sintered by air sucked in the direction indicated by arrows 36 through wind boxes 31, wind legs 32 and a duct 33. The sintering machine palette 9 is formed of a sprocket 7 on the driving side and a sprocket 11 on the discharging side. The sucked waste gas passes through a dust collector 34, comes to a sucking fan 35 and is discharged into a chimney. On the other hand, the completedly red sintered ores leave the sintering machine palette 9 and drop onto a sintered ore receiver 10 as indicated by the arrows 4, are crushed to be of any desired size (less than 150mm), by means of a crusher l2 and a receiving teeth 13 move in the direction indicated by an arrow 29 by sliding on a chute l4. Thereupon, they are sieved with 8mm.-meshes (which meshes are changed to about 5 to 8mm.) through a hot screen 15 (which screen has disadvantages such as a high frequency in causing troubles and a high maintenance cost because of high quality heat-resisting materials such as special steels being used), move in the direction indicated by an arrow 30 and are fed into a cooler 19 by a vibrating feeder 16 (the coolers may be largely classified into two kinds of a linear type and a cylindrical type. However, the cylindrical type shall be explained here). The sintered ores having still a temperature of about 800 C are bit by bit cooled by air sucked by cooling fans 20 and are fed to a cold screen 24 as indicated by an arrow 23 through a discharged ore hopper22 at a cooled surface temperature of about 150 to 200 C.

Then, the sintered ores are sieved with meshes of about 5 to 8mm. through the cold screen 24. Those on the sieve are conveyed to a blast furnace by means of a conveyer 25 as indicated by the arrow. On the other hand, those below the sieve are conveyed to a heatproof conveyer 18 for hot powders below the sieve by means of a conveyer 27 as indicated by the arrow through a hopper 26 for powders below the sieve, are joined with the hot powder sieved through the hot screen 15 and are returned to be reused. 17 is a hopper for temporarily storing hot powders below the sieve. The heatproof devices in this process are not only the sintering machine body but also the sintered ore receiver l0, crusher 12, receiving teeth 13, chute 14, hot screen 15, hopper 17 for powders below the sieve, vibrating feeder l6, cooler 19 and conveyer 18 for (hot) powders below the sieve. Recently, in the case of building a large sintering equipment (of about 6,000 tons/- day), though there is no problem in the construction of the sintering machine body, there are problems in the design and construction of the above described crushing equipment, hot screen and heat-proof conveyer. Therefore, there is an increasing trend of treating them by using devices of half the capacity arranged in a row. On the other hand, however, there are various disadvantages in the recent conventional process that, as an increase in heatproof devices used in the process as above mentioned means a cause of troubles, thereby the operation will he often suspended the production efficiency will be reduced and the maintenance cost will become high and further that, also in the quality, as sintered ores having a temperature of about 800 C (the maximum temperature part being at about l,l00 C) are quickly crushed with a crusher, the powder rate will be increased, the yield will be reduced and at the same time the sintered ore will become likely to be powdered.

SUMMARY OF THE INVENTION The present invention relates to a sintering process which eliminates such disadvantages as are described above and can be adapted to any large sintering machine and is characterized by extending a belt-shaped sintering machine (such as, for example, a Dwight- Lloyd type sintering machine) to leave a cooling zone so that a conventional cooler, hot screen and hot conveyer may be eliminated or the cooler may be simplifled to be of a very small capacity, the temperature of sintered ores at the end of the cooling zone may be preferentially controlled to an optimum temperature, to which normal conveying devices are endurable and a point, at which the sintering is completed, may be maintained in an optimum position.

Specifically the present invention is characterized in that, first, in a belt-shaped sintering machine, sintered ores as completely sintered are cooled as they are on a palette to reduce the temperature of said sintered ores so as to have cracks in more than two-thirds the sintered layer in the vertical direction in the final period of the cooling, second, in a belt-shaped sintering machine, sintered ores as completely sintered are cooled as they are on a palette, the temperature of the sintered ores is detected in the final period of the cooling and said detected temperature is preferentially controlled so as not to be above a set temperature and, third, in a belt-shaped sintering machine, a sectioning point on a regulating zone provided intermediately between a sintering zone and a cooling zoneis moved so as to coincide with a point, at which sintering of ores is to be completed, whereby, the section on the side of the sintering zone from the sectioning point on said regulating zone is made to belong to the sintering zone, while the section on the side of the cooling zone'from the sectioning point on said regulating zone is made to belong to the cooling zone and sintered ores as completely sintered are cooled as they are by being moved on a palette from the sintering zone to the cooling zone.

BRIEF DESCRIPTION OF THE DRAWINGS The subject matter of the present invention shall be explained in the following with reference to the drawings in which:

FIG. 1 is an explanatory view of a generally adopted conventional sintering process;

FIG. 2 is an explanatory view of a sintering process having a cooling zone showing an embodiment of the present invention;

FIG. 3 is an explanatory view showing another embodiment of the present invention and FIG. 4 is a waste gas temperature curve diagram showing the transition of the sintered state in the process of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The constitution and operation of the present invention shall be explained in detail with reference to FIG. 2. A mixed raw material 37 to be sintered is fed into a charging hopper 38 and is then fed onto a sintering machine palette 67 through a sloping plate 41 in the direction indicated by arrows 40 by the rotation of a drum feeder 39. A charged raw material layer 43 is ignited by an igniting furnace 42 while being gradually moved in the direction indicated by the arrows 40 by a palette 67 and is sintered by air sucked in the direction indicated by arrows 72 through wind boxes 55, wind legs 60 and a duct 71 until it arrives at regulated wind boxes 56A. The'sintered ores which have arrived at the wind boxes 56A are ina state in which a red-hot layer has perfectly reached the grate of the palette 67. The range indicated by an arrow 44 is a usually generally used sintering zone, and the range indicated by an arrow 46 is a cooling zone. The range indicated by an arrow 45 is a regulating zone which may belong either to the sintering zone or to the cooling zone.

Normally the cooling zone is to be connected with the sintering zone by extending the sintering palette as exemplified in FIG. 2. However, even if the cooling zone is made to follow the sintering zone by the use of a conveying system of a different system, it willnot deviate from the spirit of the present invention.

The sintered ores which have arrived the regulating wind boxes 56A further move to cooling regulating wind boxes 56B and enter the cooling zone 46. In said cooling zone 46, air is sucked in the direction indicated by an arrow 73 through wind boxes 56B and 57, wind legs 61 and 66 and a duct 69 to cool the sintered ores and the moving velocity of the palette 67 is controlled so that the temperature of the waste gas temperature detector 70 of the final wind box may be a desired optimum temperature (150 to 200 C in the actual operation). It is needless to say that, in such case, a wind volume or any other controllable condition may be used.

The thus controlled sintered ores are cooled to 150 to 200 C, are discharged in the direction indicated by the arrows 40, drop into a sintered ore receiver 50 and are crushed by a crusher 47 and receiving teeth 48. In fact, however, as the ores are cooled as completely sintered, there are substantially no such large blocks as are crushed by the crusher in the sintered ores. They are spontaneously arranged in the sizes of about 50 to 100mm. by cracks caused by circular shrinkages. The sintered ores which have passed through the crusher 47 are fed to a cold screen 51 through a chute 49 and are here sieved with 8mm. meshes (which meshes are changed to to 8mm.). The ores remaining on the sieve are conveyed by a conveyer 52 as a raw material in a blast furnace. On the other hand, the powder below the sieve is once stored in a hopper 53 for powders below the sieve and is returned by a conveyer 54 so as to be reused.

Further, in the case of the embodiment shown in FIG. 3, the sintered ores sieved with 8mm. meshes and remaining on the sieve are moved in the direction indicated by an arrow 52 by a vibrating feeder and are fed to a cooler 86.

The sintered ores in a temperature range of about 500 to 300 C fed into the illustrated cylindrical cooler 86 are sucked by cooling fans 87, are cooled so that the surface temperature may be below I50 C and are fed to a cold screen as indicated by an arrow 89 through a discharged ore hopper 88.

The cooler 86 need not be such standard one as is shown in the drawing. Even when providing an ordinary conveyer with a cooling fan and a hood, the object will be able to be well attained.

On the cold screen 90, the ores are sieved with meshes of about 5 to 8mm. Those on the sieve are conveyed to a blast furnace by a conveyer 91, while those below the sieve are conveyed by a conveyer 93 from a hopper 92 to join with the powder below the sieve voming from the hopper 53 so as to be reused.

81 is a dust remover for a sintering fan 83. 80 is a dust remover for a cooling fan 84. 58 is a driving sprocket wheel. 59 is a sprocket wheel on the ore discharging side.

The process of the present invention is characterized in that sintering and a part of cooling are continuously carried out in the. state of the sintering of ores being completed on a palette in such flow as shown above, or further a part of the rest is cooled by a small-sized cooler or a conveyer instead of a cooling device. The point of absolute importance in this process is that the temperature of the waste gas temperature detector 70 of the final wind box 57 must never exceed the desired temperature.

That is, as the capacity of cooling device and conveying device are not designed for high temperatures, troubles must be expected to occur if the sintered ores are discharged at a high temperature. Therefore, the temperature of the temperature detector 70 of the final wind box 57 is an important point which must be controlled absolutely preferentially. However, the preferential control of this temperature can not always satisfy the condition that the red hot layer of sintered ores must have wholly reached the surface of the grate of the palette 67 before it arrives at the sectioning point of the sintering zone and cooling zone. Consequently, by setting plurality of regulating wind boxes 56A B, the position of the state in which the red hot layer of sintered ores wholly reaches the surface of the grate of the palette 67 is observed by using thermoelectric elements 82 provided in the regulating wind boxes 56A B and sintering wind boxes 55 and is controlled by regulating dampers 74, 75, 76, 77, 78 and 79 provided as positioned between the regulating wind boxes 56 and by dampers 62, l3, l4 and 65 provided in wind legs 61 so that said position may coincide with the sectioning point of the sintering zone and cooling zone. For example, when the regulating damper 74 is made the sectioning point of the sintering zone and cooling zone, said regualting damper 74 may be operated, after closing the dampers 62 and 63, and the previously set re gulating damper 76 may be opened. The reason for carrying out such control is that because of the fan 83 for the sintering zone and the fan 84 for the cooling zone being essentially different from each other, for example, the negative suction pressure being 1,400mm. Aq. in the case of the fan 83 while about l,00Omm.Aq. in the case of the fan 84, and further also the wind volume being different between them, for instance, 85 to 90 Nm"/min/m in the case of the sintering zone, while 100 Nm /min/m in the case of the cooling zone, it is necessary to carry out such control as above mentioned in order to make the optimum use conforming to the object and to attain the maximum efficiency.

The temperature of the sintered ores in the final period of cooling may be detected by any other normally used means.

The above described position control of a point at which the sintering is completed shall be explained with reference to FIG. 4. If the waste gas temperature is being so controlled as to be maintained within a set range d in the final wind box position i, the variations of the typical sintered state will be represented by such variations as the waste gas temperature curves a, b and c caused by changes in the condition of the raw material, amount of the added fuel and amount of added water.

It is evidently seen from FIG. 4 that in the case of the curve a the sectioning point of the sintering zone and cooling zone should be placed immediately after the position of the line f (on the ore discharging side) in the case of the curve b immediately after the position of the line g and in the case of the curve c immediately after the position of the line h.

That is to say, in order to always aim at an operation high in the productivity and obtain sintered ores of a high quality, such control as is described above is necessary and indispensable.

The present invention can be adapted to any largesized sintering machine. Further, according to the pres ent invention, as sintered ores are discharged always at a temperature below 500 C (to which temperature is not limited the invention), contraction due to cooling will occur and cracks will be produced over more than two-thirds the sintered layer in the vertical direction, whereby powdering may be prevented and sintered ores may be obtained at a high yield (because it is not necessary to use a strong external force in crushing them in a product treating system) and, as sintered ores, whose maximum temperature is near 500 C, are discharged, there will be obtained sintered ores of a remarkably high quality, including no unsintered part at all. Further, the present invention has various advantages that such expensive equipments as a cooler, hot screen and heatproof conveying mechanism are not required, and even if a cooler is to be provided, it may be sufficient with a very simple one, because there is no need of making the cooling efficiency so high, and any ordinary conveying devide may be well used as such by adding only some modifications thereto, resulting in a considerable reduction in construction costs What is claimed is:

l. A method of controlling a sintered process for sintering a powdered ore in a belt-shaped sintering machine provided with a cooling zone in succession to a sintering zone and with a regulating zone overlapping both of said cooling and sintering zones, said regulating zone having a regulating means such as a damper for regulating the respective lengths of the sintering zone and the cooling zone, comprising:

controlling the sintering machine by means of said regulating means in the regulating zone such that the sintering zone and the cooling zone intersect at a point where the sintering of said ore is complete;

transferring said sintered ores when said ores are completely sintered from the sintering zone to the cooling zone;

cooling said sintered ores on a palette of said sintering machine such that cracks are produced in the sintered ore layer on said palette in the vertical direction thereof in the final portion of the cooling process;

detecting the temperature of the sintered ores by means of a temperature detecting means installed near an exit of the cooling zone; and

controlling the detected temperature so as not to exceed a predetermined temperature. 

